This invention relates to apparatus for the separation of solids, liquid and foam such as required in floatation cells and thickeners in the mining industry and more particularly to an inclined membrane separator. In the present invention foam may also be removed from the liquid by floatation. The separation of suspended solid particles from the liquid is effected by the action of gravitational forces causing settlement of the suspended particles. In the past, this natural process has long been used in industry for clarifying water. In its simplest form, an inflow of water is introduced into a tank, suspended particles drop to the bottom where they are collected and removed, and the clear water overflows into a trough outside the upper edge of the tank. It is apparent that the rate of removal of clarified water is dependent, in part, on the horizontal settling area of the tank. The larger the tank, the more clarified water that may be removed. In a further development, instead of increasing the tank size, a more complex system uses stacked metal plates one above the other, each plate acting as a fractional part of the tank bottom, and each adjacent pair of plates normally forming an individual plate compartment. The sum of the projected areas of all the plates is the equivalent total settling area. In order to remove the particles that have settled out on each plate, the plates are inclined, thus enabling the sediment of slide off to a collecting hopper. Such clarifiers are available in industry and are known as lamella gravity settlers, inclined plate clarifiers, or plate separators. Hereinafter all such units will be referred to as settlers.
In these previous continuous operation plate settlers, the efficiency is dependent on the success with which the unit achieves separation of the sediment from the clarified liquid within each plate compartment without allowing the sediment which is sliding along and off each plate to remix with either the clarified liquid or the inflowing suspension. Furthermore, for maximum efficiency the suspension must be supplied equally and uniformly to all plate compartments; similarly the clarified liquid must be removed equally and uniformly from each and every plate compartment. Designs that do not efficiently provide the above requirements result in the necessity of using larger and therefore heavier units containing more settlement plates to make up for lower efficiency. The plates that form the compartments are the primary contributors to the weight and/or cost of the whole unit and the previous apparatus all involve costly, heavy and often complex rigid plate design.
The prior art may be divided into two distinct groups or approaches in the design of continuous operation settlers. In the first group the inflowing suspension, the settling sediment and the clarified liquid all move in a generally parallel direction either upward or downward between the inclined plates forming the plate compartment. The settling sediment can only move in a downward direction and must therefore leave through the bottom of the plate compartment. Because inflow and outflow liquid are involved as well, a second product must also either leave or enter at the bottom of the plate compartment, which creates a complication. For the separation of the two products involved at the bottom of the compartment some designs require complex troughs, secondary plates, feed tubes, drain tubes, and the like, connecting to each and every compartment. Examples of these settlers are described and illustrated in the following patents:
______________________________________ U.S. 1,825,550 Sept. 29, 1931 J. Schulte 2,077,057 Apr. 13, 1937 J. W. Poole 2,498,292 Feb. 21, 1950 J. J. Naugle 2,793,186 May 21, 1957 B. A. Dunell et al 3,182,799 May 11, 1965 M. Krofta 3,272,341 Sept. 13, 1966 R. T. Hukki 3,494,475 Feb. 10, 1970 B. Hedstrom et al 3,552,554 Jan. 5, 1971 G. Olgard 3,687,298 Aug. 29, 1972 J. Rozkydalek 3,754,656 Aug. 28, 1973 Horiguchi et al 3,886,064 May 27, 1975 P. E. Kosonen 3,894,955 July 15, 1975 B. Forsell Canadian 956,249 Oct. 15, 1974 G. Weijman-Hane ______________________________________
Other designs attempt to simplify the separation of two of the products by the use of settler plates that contain corrugations, ridges, or other patterns, and may contain punched holes therein as well. Such units are described in the following U.S. Patents:
______________________________________ 367,308 July 26, 1887 W. Macnab et al 3,346,122 Oct. 10, 1967 J. Cornelissen 3,666,112 May 30, 1972 Pielkenrood et al 3,768,648 Oct. 30, 1973 Anderson et al 3,813,851 June 4, 1974 T. Eder 3,837,501 Sept. 24 1974 J. Pielkenrood 3,847,813 Nov. 12, 1974 J. L. Castelli 3,849,311 Nov. 19, 1974 P. Jakubek et al 3,928,209 Dec. 23, 1975 Engdahl et al 4,028,256 June 7, 1977 J. Pielkenrood ______________________________________
Still other settler designs subdivide the plate compartments into tubular units, thereby reducing cross-currents but increasing the complexity of the construction.
______________________________________ 3,491,892 Jan. 27, 1970 C. E. McCann 3,615,025 Oct. 26, 1971 A. H. Rice et al 3,768,648 Oct. 30, 1973 Anderson et al 3,852,199 Dec. 3, 1974 Wachsmuth et al 3,898,164 Aug. 5, 1975 A. K. Hsiung 3,923,659 Dec. 2, 1975 H. Ulrich 3,975,276 Aug. 17, 1976 L. A. Schmid ______________________________________
The second group or approach in the design of settlers includes all cross-flow settlers where the sediment moves and slides generally at right angles to the flow direction of the suspension and clarified liquid. This approach removes the necessity of having to provide special means for separating two of the products at the bottom of the plate compartment as was necessary in the first described category of settlers. Uniform distribution of the inflowing suspension to all plate compartments still remains a problem and attempts are made to solve it by various fixed baffle arrangements, perforated plates, and the like. While representing an improvement over the previous group of settlers, this apparatus remains relatively costly, cumbersome and heavy for large volume applications. Patents illustrating this approach are:
______________________________________ U.S. 1,732,386 Oct. 22, 1929 M. Sprockhoff 2,119,013 May 31, 1938 F.W. Kerns 2,868,384 Jan. 13, 1959 I.E. Puddington 3,903,000 Sept. 2, 1975 Miura et al Canadian 962,199 Feb. 4, 1975 A.B. Turner ______________________________________